1. Field of the Invention
The present invention relates to a video calling method for a mobile communication system, and more particularly to a video calling method that can provide video images of a video call, which are transmitted from a Voice over Internet Protocol (VoIP) network, through a third display device.
2. Description of the Related Art
VoIP is a technology that provides a voice service, which has been provided through a public switched telephone network (PSTN), by using an Internet protocol. By using an IP network, diverse services, which are not provided through the existing telephone network (PSTN), can be provided. Representative applications of such services may, for example, be a web call center, an instant message, a computer telephony integration (CTI), a unified messaging system (UMS), and diverse applications that are served or to be served.
At present, a VoIP structure is composed of a gateway, a terminal, and a call connection agent. The gateway connects a PSTN with an IP network, so that the networks can communicate with each other, and the call connection agent controls the gateway by using a media gateway control protocol (MGCP). In the VoIP network, H.323 and a session initiation protocol (SIP) are basically used as signaling protocols.
On the other hand, in 3rd generation mobile communication systems using International Standard (IS)-95B and 95C, the importance of a data link becomes greater, as diverse services are proposed and used. Among such services, a video call is a technology that enables communication devices to communicate audio and video images with each other, and is expected to be the center of services using mobile communication terminals.
In particular, in an ALL-IP-based mobile communication system, it is expected that more diverse types of video calling services will be possible.
FIG. 1 is an exemplary view illustrating the construction of a conventional video calling system.
As illustrated in FIG. 1, two mobile communication terminals (referred to as terminal A and terminal B) 11 and 12 are connected to each other through a channel 101 for transmitting voice or audio data and a channel 102 for transmitting video data. The voice and video data may be produced through microphones and cameras of the respective mobile communication terminals 11 and 12 and transmitted to each other through the respective channels 101 and 102. In this manner a video call is made through the mobile communication terminals.
Also illustrated is that the respective channels 101, 102 are connected to the terminals 11, 12 through a VoIP network 100.
The conventional video calling system as described above enables a mobile communication terminal 11, for example, to transmit voice data and video data to an opposite mobile communication terminal, i.e., 12, and thus users of the respective mobile communication terminals can exchange audio and video images with each other.
However, the conventional video calling system as described above has a drawback in that its destinations are limited to the respective mobile communication terminals, and thus each user must hold a camera in his/her hand in order to provide a video to the opposite party while he/she is making a video call.
In addition, the conventional video calling system has the problem in that since the display screen of the mobile communication terminal is small, video images of a high picture quality that have been received from the opposite party cannot be displayed on the display screen with the high picture quality maintained.